FFP at the very least makes it more risky/difficult and more expensive. If you have to swallow the kind of fine City got that's significant and essentially means that new owners would only actually get a portion of what they spend put into the club.
More important is the fact that new owners would have to spend a ****load of money just to get us to parity with City, Chelsea (and United when/if they rebound). No guaranteed titles, not even guaranteed CL football for quite a few years. As we've seen recently investors have gone for clubs in other leagues, Malaga, PSG, Monaco, Anzhi etc instead of PL clubs. Some of those have worked out, others not so much, but none of them have gone for PL clubs. I think that's worth noting.
I don't think it's likely that a Chelsea/City story is on our horizon if Lewis sells out at this point.